"ACM Queen Miranda Lambert Dishes on Her Good-Luck Charm for the Big Night and the Bro-Country Trend: 'There's Room for Everyone'". Interview with Chuck Arnold, www.billboard.com. April 13, 2015.
Hermann von Helmholtz, Alexander John Ellis (1875). “On the Sensations of Tone as a Physiological Basis for the Theory of Music”, p.3, London : Longmans, Green and Company